The present invention relates to a method for producing flexible tubes and to an apparatus therefor.
GB-A-906 810 discloses an apparatus for the production of flexible tubes comprising a wrapping machine for depositing strips of rubber around an elongate hollow cylindrical core and a vulcanizer, which are arranged in series on a common axis. The wrapping machine includes a trolley, which is provided with a motor for its movement on rails and has a through hole for the passage of the core in correspondence with the common axis, and a plurality of heads which rotate about the axis and carry reels bearing the strips to be deposited.
The vulcanizer has holes in its ends in correspondence with the common axis and contains an air bag, which is fed with compressed air by a duct surrounded by the hollow core.
In the operation, a portion of flexible tube is built over the core kept out from the vulcanizer, superposing therein several strips of rubber or reinforced rubber. Then the core is retracted, the deflated air bag is inserted into the portion of green tube just built and the previously vulcanized portion of tube is pulled out from the vulcanizer, pulling the green portion of the tube into the vulcanizer through tension, transmitted by a liner which adheres externally to both tube portions. The green portion is then vulcanized around the inflated air bag and this cycle of operations is repeated until the tube becomes as long as desired.
According to GB-906 810, the green portion of the tube has to be initially supported by the core during the wrapping operation and then by the air bag during the vulcanization operation. The transfer from the first to the second supporting means constitutes a delicate step, where the easily deformable still uncured portion of the tube may be permanently damaged due to applied stresses.